Semiconductor device and manufacturing method thereof

ABSTRACT

In a method of manufacturing a negative capacitance structure, a dielectric layer is formed over a substrate. A first metallic layer is formed over the dielectric layer. After the first metallic layer is formed, an annealing operation is performed, followed by a cooling operation. A second metallic layer is formed. After the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase. The first metallic film includes a oriented crystalline layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application 62/578,919, filed Oct. 30, 2017, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to semiconductor integrated circuits, and more particularly to semiconductor devices including negative capacitance field effect transistors (NC FETs).

BACKGROUND

The subthreshold swing is a feature of a transistor's current-voltage characteristic. In the subthreshold region the drain current behavior is similar to the exponentially increasing current of a forward biased diode. A plot of logarithmic drain current versus gate voltage with drain, source, and bulk voltages fixed will exhibit approximately logarithmic linear behavior in this metal-oxide-semiconductor (MOS) FET operating region. To improve the subthreshold properties, a negative capacitance field effect transistor (NC FET) using a ferroelectric material has been proposed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1A shows a cross sectional view of a metal-insulator-semiconductor (MIS) FET-type NC FET and FIG. 1B shows a cross sectional view of a metal-insulator-metal-insulator-semiconductor (MIMIS) FET-type NC FET.

FIGS. 2A, 2B, 2C and 2D show various stages of manufacturing operations for a negative capacitance structure in accordance with an embodiment of the present disclosure.

FIGS. 3A, 3B, 3C and 3D show various stages of manufacturing operations for a negative capacitance structure in accordance with an embodiment of the present disclosure.

FIGS. 3E and 3F show various stages of manufacturing operations for a negative capacitance structure in accordance with another embodiment of the present disclosure.

FIGS. 4A, 4B, 4C and 4D show various atomic structures of HfO₂. FIG. 4E shows X-Ray Diffraction (XRD) measurement results.

FIGS. 5 and 6 show electron energy loss spectroscopy (EELS) measurement results.

FIGS. 7A, 7B, 7C and 7D show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 8A, 8B, 8C and 8D show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 9A, 9B and 9C show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 10A, 10B and 10C show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 11A, 11B and 11C show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 12A, 12B and 12C show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 13A, 13B, 13C and 13D show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

FIGS. 14A, 14B, 14C and 14D show manufacturing operations for an NC FET in accordance with another embodiment of the present disclosure.

FIGS. 15A, 15B, 15C and 15D show manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific embodiments or examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, dimensions of elements are not limited to the disclosed range or values, but may depend upon process conditions and/or desired properties of the device. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Various features may be arbitrarily drawn in different scales for simplicity and clarity. In the accompanying drawings, some layers/features may be omitted for simplification.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. In addition, the term “made of” may mean either “comprising” or “consisting of.” Further, in the following fabrication process, there may be one or more additional operations in/between the described operations, and the order of operations may be changed.

To lower subthreshold swing (S.S.) of a field effect transistor (FET), a negative-capacitance (NC) technology, such as integrating ferroelectric (FE) materials, provides a feasible solution to lower V_(DD) (power supply) significantly, and achieves an FET having a steep S.S. for low power operation.

In an NC FET, a capacitor (e.g., a ferroelectric (FE) capacitor) having a negative capacitance is connected to a gate of a MOS FET in series. The ferroelectric negative capacitor can be a separate capacitor connected by a conductive layer (e.g., wire/contact) to the gate of the MOS FET, in some embodiments. In other embodiments, one of the electrodes of the negative capacitor is a gate electrode of the MOS FET. In such a case, the negative capacitor is formed within sidewall spacers of the MOS FET.

In conventional devices, high-K gate materials, such as HfO₂, are usually an amorphous layer. However, the un-doped HfO₂ is amorphous and paraelectric, which does not show a negative-capacitance effect. Ferroelectric materials having Perovskite structure, such as PZT or BaTiO₃, have excellent FE characteristics. However, these materials still pose difficulties because formation of these materials is not fully compatible with silicon-based semiconductors, and the ferroelectric properties degrade with reducing the thickness thereof due to a size effect.

In the present disclosure, a doped HfO₂ layer having an orthorhombic crystal phase, which shows a ferroelectric property, and its production methods are provided. In addition, in the present disclosure, the crystal orientation of the doped HfO₂ layer is controlled to achieve a largest ferroelectric effect by controlling the doped HfO₂ intrinsic polarization to be parallel coupled with the external electric-field from a gate electrode. To control the crystal orientation, at least one of a bottom crystal structure control layer and an upper crystal structure control layer is provided.

FIG. 1A shows a cross sectional view of a cross sectional view of metal-insulator-semiconductor (MIS) FET-type NC FET, and FIG. 1B shows a cross sectional view of a metal-insulator-metal-insulator-semiconductor (MIMIS) FET-type NC FET. Although FIGS. 1A and 1B show NC FETs of a planar MOS transistor structure, fin FETs and/or gate-all-around FETs can be employed.

As shown in FIG. 1A, an MIS NC FET includes a substrate 100, a channel 101 and source and drain 102. The source and drain 102 are appropriately doped with impurities. Further, the source and drain and the channel (active regions) are surrounded by an isolation insulating layer (not shown), such as shallow trench isolation (STI), made of, for example, silicon oxide.

An interfacial layer 103 is formed over the channel layer 101, in some embodiments. The interfacial layer 103 is made of silicon oxide having thickness in a range from about 0.5 nm to about 1.5 nm in some embodiments.

A ferroelectric dielectric layer 105 is disposed over the interfacial layer 103. The ferroelectric dielectric layer 105 includes HfO₂ doped with one or more elements selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr. In some embodiments, the ferroelectric dielectric layer 105 includes HfO₂ doped with Si and/or Zr. In certain embodiments, the ferroelectric dielectric 105 layer includes HfO₂ doped with Zr, such as HfZrO₂ (Hf:Zr=1:1). Further, in other embodiments, the ferroelectric dielectric 105 layer includes HfO₂ doped with Al at a concentration in a range from about 7 mol % to about 11 mol %. In the present disclosure, the ferroelectric dielectric layer 105 includes an orthorhombic crystal phase, which is (111) oriented. A (111) orientated layer means that the main surface (the surface parallel to the surface of a substrate on which the layer is formed) has a (111) crystal surface (i.e., having a normal vector parallel to a <111> direction). The orthorhombic crystal of the ferroelectric dielectric layer 105 is substantially single crystalline or the majority of the crystalline phases is (111) oriented crystals, in some embodiments. In other embodiments, the orthorhombic crystal of the ferroelectric dielectric layer 105 is (111) oriented polycrystalline. The orthorhombic crystal phase identification and (111) orientation identification and can be determined by X-ray diffraction (XRD) patterns. The orthorhombic crystal phase identification and (111) orientation identification of a specific crystal grain can be detected by a precession electron diffraction (PED) technique, which can detect a preferred orientation of each crystal grain and interlayer spacing of layers (d-spacing). The thickness of the ferroelectric dielectric layer 105 is in a range from about 1.0 nm to about 5 nm in some embodiments.

A gate electrode layer 106 is disposed over the ferroelectric dielectric layer 105. The gate electrode layer 106 includes one or more metallic layers. In some embodiments, the gate electrode layer 106 includes a first conductive layer (a capping layer) disposed on the ferroelectric dielectric layer 105, a second layer (a barrier layer) disposed on the first conductive layer, a third conductive layer (a work function adjustment layer) disposed on the second conductive layer, a fourth conductive layer (a glue layer) disposed on the third conductive layer and/or a fifth conductive layer (a main gate metal layer) disposed on the fourth conductive layer.

The capping layer includes a TiN based material, such as TiN and TiN doped with one or more additional elements. In some embodiments, the TiN layer is doped with Si. The barrier layer includes TaN in some embodiments.

The work function adjustment layer includes one or more layers of conductive material, such as a single layer of TiN, TaN, TaAlC, TiC, TaC, Co, Al, TiAl, HfTi, TiSi, TaSi or TiAlC, or a multilayer of two or more of these materials. For the n-channel FinFET, one or more of TaN, TaAlC, TiN, TiC, Co, TiAl, HfTi, TiSi and TaSi is used as the work function adjustment layer, and for the p-channel FinFET, one or more of TiAlC, Al, TiAl, TaN, TaAlC, TiN, TiC and Co is used as the work function adjustment layer.

The glue layer includes Ti, TiN and/or TaN in some embodiments. The main gate metal layer includes a metal selected from a group of W, Cu, Ti, Al and Co.

Further, sidewall spacers 109 are formed on opposing side faces of the gate structure as shown in FIG. 1A. The sidewall spacers 109 include one or more layers of insulating material, such as silicon oxide, silicon nitride and silicon oxynitride.

In FIG. 1B, similar to FIG. 1A, a channel 101 and source and drain 102 are formed on a substrate 100. A first gate dielectric layer 113 is disposed over the channel 101. The first gate dielectric layer 113 includes one or more high-k dielectric layers (e.g., having a dielectric constant greater than 3.9) in some embodiments. For example, the one or more gate dielectric layers may include one or more layers of a metal oxide or a silicate of Hf, Al, Zr, combinations thereof, and multi-layers thereof. Other suitable materials include La, Mg, Ba, Ti, Pb, Zr, in the form of metal oxides, metal alloy oxides, and combinations thereof. Exemplary materials include MgO_(x), SiN (Si₃N₄), Al₂O₃, La₂O₃, Ta₂O₃, Y₂O₃, HfO₂, ZrO₂, GeO₂, Ga₂O₃, Gd₂O₃, TaSiO₂, TiO₂, HfSiON, YGe_(x)O_(y), YSi_(x)O_(y) and LaAlO₃, and the like. In certain embodiments, HfO₂, ZrO₂ and/or Hf_(x)Zr_(1-x)O₂ is used. The formation methods of first gate dielectric layer 113 include molecular-beam deposition (MBD), atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), and the like. In some embodiments, the first gate dielectric layer 113 has a thickness of about 1.0 nm to about 5.0 nm.

In some embodiments, an interfacial layer (not shown) may be formed over the channel 101 prior to forming the first gate dielectric layer 113, and the first gate dielectric layer 113 is formed over the interfacial layer.

A first gate electrode 114 as an internal electrode is disposed on the first gate dielectric layer 113. The first gate electrode 114 may be one or more metals, such as W, Cu, Ti, Ag, Al, TiAl, TiAlN, TaC, TaCN, TaSiN, Mn, Co, Pd, Ni, Re, Ir, Ru, Pt, and Zr. In some embodiments, the first gate electrode 114 includes one or more of TiN, WN, TaN, and Ru. Metal alloys such as Ti—Al, Ru—Ta, Ru—Zr, Pt—Ti, Co—Ni and Ni—Ta may be used and/or metal nitrides, such as WN_(x), TiN_(x), MoN_(x), TaN_(x), and TaSi_(x)N_(y) may also be used. In some embodiments, at least one of W, Ti, Ta, TaN and TiN is used as the first gate electrode 114. In some embodiments, the first gate electrode 114 includes a work function adjustment layer.

A ferroelectric dielectric layer 115 is formed on the first gate electrode 114. The ferroelectric dielectric layer 115 is substantially the same as the ferroelectric dielectric layer 105.

Further, a second gate electrode 116 as an external gate is disposed on the ferroelectric dielectric layer 115. The second gate electrode 116 may be a metal selected from a group of W, Cu, Ti, Ag, Al, TiAl, TiAlN, TaC, TaCN, TaSiN, Mn, Co, Pd, Ni, Re, Ir, Ru, Pt, and Zr. The second gate electrode 116 is made of the same material as or different material from the first gate electrode 114. Further, sidewall spacers 119 are formed on opposing side faces of the gate structure as shown in FIG. 1B. The sidewall spacers 119 include one or more layers of insulating material, such as silicon oxide, silicon nitride and silicon oxynitride.

As shown in FIGS. 1A and 1B, the ferroelectric dielectric layers 105 and 115 and the first gate dielectric layer 113 have a “U-shape” in the cross section, having a thin center portion and thick side portions in the vertical direction.

FIGS. 2A, 2B, 2C and 2D show various stages of manufacturing operations for a negative capacitance structure in accordance with an embodiment of the present disclosure. It is understood that additional operations can be provided before, during, and after the processes shown by FIGS. 2A-2D, and some of the operations described below can be replaced or eliminated, for additional embodiments of the method. The order of the operations/processes may be interchangeable. Material, configuration, dimensions and/or processes the same as or similar to the foregoing embodiments described with FIGS. 1A and 1B may be employed in the following embodiments, and detailed explanation thereof may be omitted.

As shown in FIG. 2A, an interfacial layer 20 is formed on a substrate 10. In some embodiments, the substrate 10 is made of a suitable elemental semiconductor, such as silicon, diamond or germanium; a suitable alloy or compound semiconductor, such as Group-IV compound semiconductors (silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), GeSn, SiSn, SiGeSn), Group III-V compound semiconductors (e.g., gallium arsenide (GaAs), indium gallium arsenide (InGaAs), indium arsenide (InAs), indium phosphide (InP), indium antimonide (InSb), gallium arsenic phosphide (GaAsP), or gallium indium phosphide (GaInP)), or the like. Further, the substrate 10 may include an epitaxial layer (epi-layer), which may be strained for performance enhancement, and/or may include a silicon-on-insulator (SOI) structure.

In some embodiments, the interfacial layer 20 is a silicon oxide, which may be formed by chemical reactions. For example, a chemical silicon oxide may be formed using deionized water+ozone (DIO₃), NH₄OH+H₂O₂+H₂O (APM), or other methods. Other embodiments may utilize a different material or processes for the interfacial layer. In some embodiments, the interfacial layer 20 has a thickness of about 0.5 nm to about 1.5 nm.

Then, a dielectric layer 30 is formed over the interfacial layer 20. The dielectric layer 30 includes HfO₂ doped with one or more elements selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr.

The formation methods of the dielectric layer 30 include molecular-beam deposition (MBD), atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), and the like. In some embodiments, HfO₂ doped with Zr can be formed by ALD using HfCl₄ and H₂O as a first precursor and ZrCl₄ and H₂O as a second precursor at a temperature in a range from about 200° C. to 400° C. In a case of HfO₂ doped with Si, SiH₄, Si₂H₆, and/or SiH₂Cl₂ or other suitable silicon source gas may be used. The dielectric layer 30 as deposited is amorphous and paraelectric. The thickness of the dielectric layer 30 is in a range from about 1 nm to about 5 nm in some embodiments.

After the dielectric layer 30 is formed, a capping layer 40, as an upper crystal structure control layer, is formed on the dielectric layer 30, as shown in FIG. 2B. The capping layer 40 includes a TiN based material, such as TiN and TiN doped with one or more additional elements, in some embodiments. In some embodiments, the TiN layer is doped with Si. The capping layer 40 can be formed by ALD, CVD or physical vapor deposition including sputtering or any other suitable methods. The thickness of the capping layer 40 is in a range from about 1 nm to about 5 nm in some embodiments.

In the present disclosure, the TiN-based capping layer 40 includes crystal grains that are (111) and/or (220) oriented. The (111) and (220) orientation of the capping layer 40 can facilitate controlling the crystal orientation of the HfO₂ layer to have a (111) orientation. The TiN-based capping layer 40 can be formed by an ALD. As-deposited in one deposition step in the ALD, the TiN-based layer forms a monoatomic layer in a close-packed configuration (i.e., (111) oriented), with a high density. In some embodiments, the monoatomic layer shows (200) and/or (220) orientation with a lower density. After the annealing operation, when observed by an X-ray diffraction method, a (111) signal becomes more clear and sharper even though (200) and/or (222) are also observed.

In some embodiments, the TiN-based capping layer 40 can be formed by using TiCl₄ and NH₃ as precursors, with Ar as a carrier gas, at a temperature in a range from about 350° C. to about 450° C. In some embodiments, a Si doping gas, such as SiH₄, is added. By controlling ALD conditions and an annealing temperature, it is possible to control the crystalline orientation of the TiN-based capping layer 40 to be (111) oriented. In other embodiments, TaN and/or W, which also has a controlled crystal orientation, is used as the capping layer 40.

After the capping layer 40 is formed, an annealing operation is performed as shown in FIG. 2C. The annealing operation is performed at a temperature in a range from about 700° C. to about 1000° C. in an inert gas ambient, such as N₂, Ar and/or He. The annealing period is in a range from about 10 sec to 1 min in some embodiments. After the annealing, a cooling operation is performed. In some embodiments, the substrate is cooled down to less than 100° C. or to room temperature (about 25° C.). The annealing operation after the capping layer 40 is formed provides driving a force for the Zr-doped HfO₂ structure transition from amorphous phase to high-temperature tetragonal phase, which is (111) oriented, and capping layer 40 provides the mechanical stress needed for the crystalline transition from the high-temperature tetragonal phase to the high-pressure ferroelectric orthorhombic phase during cooling. Due to the crystalline orientations of the capping layer 40 (i.e., (111) and (220)), the (111) oriented doped-HfO₂ layer 30 can be obtained.

When a transmission electron microscopy (TEM) image is taken, it was observed that the irregularity of the TiN-based capping layer coincides with the Zr-doped HfO₂ grain boundary directly above, which indicates that the polycrystalline structure of the TiN-based capping layer influences the growth direction and the orientation of the Zr-doped HfO₂ during the post annealing and cooling.

In some embodiments, after the capping layer 40 is formed, an amorphous silicon layer is formed on the capping layer 40, and then the annealing operation is performed. After the annealing operation and cooling operation are performed, the amorphous silicon layer is removed.

After the cooling operation, a barrier layer 52 made of, for example, TaN, is formed over the capping layer 40, as shown in FIG. 2D. The barrier layer 52 can be formed by ALD, CVD or physical vapor deposition including sputtering or any other suitable methods. When ALD is utilized, the ALD is performed at a temperature in a range from about 300° C. to about 400° C. in some embodiments. The thickness of the barrier layer 52 is in a range from about 1 nm to about 5 nm in some embodiments. In some embodiments, the annealing operation to convert the amorphous structure to the orthorhombic structure may be performed after the barrier layer 52 is formed.

Further, a work function adjustment layer 54 is formed on the barrier layer 52. In some embodiments, the work function adjustment layer 54 includes TiN for a p-type transistor and TiAl for an n-type transistor. Any other suitable metallic material can be used as the work function adjustment layer 54. In some embodiments, a TiAl layer is also formed on a TiN work function adjustment layer for a p-type transistor. The work function adjustment layer 54 can be formed by ALD, CVD or physical vapor deposition including sputtering or any other suitable methods. When ALD is utilized, the ALD is performed at a temperature in a range from about 300° C. to about 400° C. in some embodiments. The thickness of the work function adjustment layer 54 is in a range from about 1 nm to about 5 nm in some embodiments.

Further, a main gate metal layer 58 is formed over the work function adjustment layer 54. The main gate metal layer 58 includes one or more metals, such as W, Cu, Ti, Al and Co, or other suitable material. In some embodiments, when the main gate metal layer 58 is W, a glue layer 56 is formed on the work function adjustment layer 54. In some embodiments, the glue layer 56 is Ti. As shown in FIG. 2D, the gate electrode 50 may include a barrier layer 52 disposed on the capping layer 40, a work function adjustment layer 54 disposed on the barrier layer 52, a glue layer 56 disposed on the work function adjustment layer 54 and a main gate metal layer 58. In some embodiments, the capping layer may be considered as a part of the gate electrode 50.

FIGS. 3A-3F show various stages of manufacturing operations for a negative capacitance structure in accordance with an embodiment of the present disclosure. Material, configuration, dimensions and/or processes the same as or similar to the foregoing embodiments described with FIGS. 1A-2D may be employed in the following embodiments, and detailed explanation thereof may be omitted. In the embodiment of FIGS. 3A-3F, instead of or in addition to the crystalline capping layer 40, a seed dielectric layer 25, as a bottom crystal structure control layer, is utilized to control the crystalline orientation of the doped-HfO₂ layer.

As shown in FIG. 3A, after the interfacial layer 20 is formed on the substrate 10, a seed dielectric layer 25 is formed before the dielectric layer 30 is formed. In some embodiments, the seed dielectric layer 25 includes a layer that can easily form a tetragonal or orthorhombic structure. In certain embodiments, ZrO₂ is used as the seed dielectric layer 25. Polycrystalline ZrO₂ easily forms a tetragonal phase, when its grain size is smaller than a critical value (e.g., 30 nm). When observed by an XRD method, an as-deposited and a post-annealed ZrO₂ film show a strong orthorhombic-phase (111) signal and a strong tetragonal-phase (011) signal. Such structures of the ZrO₂ layer are beneficial for growth of an orthorhombic-phase doped HfO₂ layer.

In some embodiments, the ZrO₂ seed layer can be formed by ALD using ZrCl₄ and H₂O as precursors with Ar or N₂ as a carrier gas. In other embodiments, tetrakis-(dimethylamino)zirconium (Zr[N(CH₃)₂]₄) with oxygen plasma together with Ar or N₂ as a carrier gas is used. The ALD is performed at a temperature in a range from about 250° C. to 300° C. in some embodiments. The thickness of the seed dielectric layer 25 is in a range from about 0.5 nm to about 2.0 nm in some embodiments and is in a range from about 0.5 nm to about 1.0 nm in other embodiments.

After the seed dielectric layer 25 is formed, the dielectric layer 30, for example, Zr-doped HfO₂, is formed on the seed dielectric layer 25, as shown in FIG. 3A. Then, similar to FIG. 2B, a capping layer 40 is formed on the dielectric layer 30. The capping layer 40 can be a crystalline orientation controlled layer as set forth above or a polycrystalline or amorphous layer.

Subsequently, similar to the operations explained with respect to FIG. 2C, after the capping layer 40 is formed, an annealing operation is performed as shown in FIG. 3C. After the annealing (and cooling) operation, the dielectric layer 30 becomes a (111) oriented crystalline layer. Due to the seed dielectric layer 25, the (111) oriented doped-HfO₂ layer 30 can be obtained. In addition, after the annealing (and cooling) operation, the seed dielectric layer 25 also becomes an orthorhombic (111) oriented ZrO₂ layer. Further, similar to the operations explained with respect to FIG. 2D, a gate electrode 50 is formed as shown in FIG. 3D. The orthorhombic crystal phase identification and (111) orientation identification of doped-HfO₂ layer 30 can be determined by X-ray diffraction (XRD) patterns. The orthorhombic crystal phase identification and (111) orientation identification of specific crystal grain can be detected by a precession electron diffraction (PED) technique, which can detect a preferred orientation of each crystal grain and interlayer spacing of layers (d-spacing).

FIGS. 3E and 3F show various stages of manufacturing operations for a negative capacitance structure in accordance with another embodiment of the present disclosure. In this embodiment, instead of forming a single layer of the doped-HfO₂ layer 30, the dielectric layer includes alternately stacked one or more HfO₂ layer 30A and one or more ZrO₂ layers 30B formed over the seed dielectric layer 25, as shown in FIG. 3E.

The alternate structure of one or more HfO₂ layer 30A and one or more ZrO₂ layers 30B can be formed by ALD. Each of the layers can be a monoatomic layer or multi-atomic layer (e.g., two or three monoatomic layers). Although FIG. 3E shows four layers of HfO₂ layer 30A and four layers of ZrO₂ layers 30B, the number of the layers is not limited to four, and it can be two, three or five or more.

After the annealing and cooling operations, the stacked layer of HfO₂ layer 30A and ZrO₂ layers 30B becomes a single layer of Zr-doped HfO₂ (HfZrO₂), having a (111) oriented orthorhombic structure, which is determined by the PED technique, as shown in FIG. 3F. In some embodiments, at least a part of the seed dielectric layer 25 is consumed to be the single layer of Zr-doped HfO₂.

FIGS. 4A, 4B, 4C and 4D show various atomic structures of HfO₂. FIG. 4A shows the amorphous structure of the doped HfO₂ as deposited. By applying heat, the amorphous structure transitions to a tetragonal crystal structure (phase), as shown in FIG. 4B. When the heated HfO₂ having a tetragonal crystal structure is cooled with a capping metal thereon, the HfO₂ becomes an orthorhombic crystal structure (phase), as shown in FIG. 4C. If the heated HfO₂ having a tetragonal crystal structure is cooled without the capping metal thereon, the HfO₂ becomes a mixture of a monolithic crystal structure (left) and a tetragonal crystal structure (right), as shown in FIG. 4D. The orthorhombic HfO₂ has a non-centrosymmetric structure, and thus spontaneous polarization is generated by four oxygen ions displacement. Accordingly, better ferroelectric properties can be obtained by the orthorhombic HfO₂.

FIG. 4E shows X-Ray Diffraction (XRD) measurement results. The samples are a 3-nm thick doped HfO₂ as deposited and a 3-nm thick doped HfO₂ after the annealing operation with a capping layer. The doped HfO₂ as deposited shows a broad spectrum indicating amorphous structure. In contrast, the doped HfO₂ after the annealing operation with a capping layer shows peaks corresponding to orthorhombic phase.

FIGS. 5 and 6 show electron energy loss spectroscopy (EELS) measurement results. As set forth above, after the dielectric layer 30 is converted to an orthorhombic phase, additional layers are formed with some thermal operations. The dopant elements in HfO₂ such as semiconductor material (Si) and metal elements (Zr, Al, La, Y, Gd and/or Sr) introduced by in-situ doping during the ALD growth are substantially uniformly distributed in the doped HfO₂ layer. As shown in FIGS. 5 and 6, Ti arising from the capping layer 40 (TiN based material) diffuses into the HfZrO₂ layer. When a TiAl layer is used as a work function adjustment layer 54 for an n-type transistor, Al may also diffuse into the HfZrO₂ layer, as shown in FIG. 5. In some embodiments, the HfZrO₂ layer includes Al in an amount of 5-7 mol %. When a TiN layer is used as a work function adjustment layer 54 for a p-type transistor, Ti originating from the TiN work function adjustment layer may also diffuse into the HfZrO₂ layer, as shown in FIG. 6. For the p-type transistor, Al may not diffuse into the HfZrO₂ layer (below a detection limit), even if a TiAl layer is formed on the TiN work function adjustment layer. In some embodiments, the HfZrO₂ layer includes Ti in an amount of 2-5 mol %.

In some embodiments, the ferroelectric HfO₂ layer consists of an orthorhombic crystal phase. In other embodiments, the ferroelectric HfO₂ layer is substantially formed by an orthorhombic crystal phase. In such a case, the orthorhombic crystal phase is about 80% or more of the ferroelectric HfO₂ layer, and the remaining phases may be amorphous, a monolithic phase and/or a tetragonal phase.

FIGS. 7A-13C show various stages of manufacturing operations for an NC FET in accordance with an embodiment of the present disclosure. It is understood that additional operations can be provided before, during, and after the processes shown by FIGS. 7A-13C, and some of the operations described below are replaced or eliminated, for additional embodiments of the method. The order of the operations/processes may be interchangeable. Material, configuration, dimensions and/or processes the same as or similar to the foregoing embodiments described with FIGS. 1A-3F may be employed in the following embodiments, and detailed explanation thereof may be omitted.

FIG. 7A shows a perspective view and FIG. 7B is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. As shown in FIGS. 7A and 7B, a substrate 200 is provided. In some embodiments, the substrate 200 is made of a suitable elemental semiconductor, such as silicon, diamond or germanium; a suitable alloy or compound semiconductor, such as Group-IV compound semiconductors (silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), GeSn, SiSn, SiGeSn), Group III-V compound semiconductors (e.g., gallium arsenide (GaAs), indium gallium arsenide (InGaAs), indium arsenide (InAs), indium phosphide (InP), indium antimonide (InSb), gallium arsenic phosphide (GaAsP), or gallium indium phosphide (GaInP)), or the like. Further, the substrate 200 may include an epitaxial layer (epi-layer), which may be strained for performance enhancement, and/or may include a silicon-on-insulator (SOI) structure. The upper portion of the substrate 200 can be multilayers of Si and SiGe.

FIG. 7C shows a perspective view and FIG. 7D is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. As shown in FIGS. 7C and 7D, fin structures 210 are formed by etching the substrate 200 and forming an isolation insulating layer 220. The fin structures 210 may be patterned by any suitable method. For example, the fin structures 210 may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers, or mandrels, may then be used to pattern the fin structures 210. In some embodiments, the width of the fin structures 210 is in a range from about 4 nm to about 10 nm and the pitch of the fin structures 210 is in a range from about 10 nm to about 50 nm.

Then, an insulating material layer 220 is formed over the fin structures, thereby embedding the fin structures. The insulating material layer 220 may be made of suitable dielectric materials such as silicon oxide, silicon nitride, silicon oxynitride, fluorine-doped silicate glass (FSG), low-k dielectrics such as carbon doped oxides, extremely low-k dielectrics such as porous carbon doped silicon dioxide, a polymer such as polyimide, combinations of these, or the like. In some embodiments, the insulating material layer 220 is formed through a process such as CVD, flowable CVD (FCVD), or a spin-on-glass process, although any acceptable process may be utilized. Subsequently, portions of the insulating material layer 220 extending over the top surfaces of the fin structures 210 are removed using, for example, an etch process, chemical mechanical polishing (CMP), or the like, as shown in FIGS. 7C and 7D.

FIG. 8A shows a perspective view and FIG. 8B is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Further, as shown in FIGS. 8A and 8B, the insulating material layer 220 is recessed so that the upper portions of the fin structures 210 are exposed. The recessed insulating material layer 220 is called an isolation insulating layer or a shallow trench isolation (STI). The height of the exposed fin structures 210 measured from the upper surface of the isolation insulating layer 220 is in a range about 30 nm to about 100 nm in some embodiments.

FIG. 8C shows a perspective view and FIG. 8D is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Subsequently, a dummy gate dielectric layer 215 is formed over the upper portions of the fin structure 210, as shown in FIGS. 8C and 8D. The dummy gate dielectric layer 215 is a silicon oxide layer formed by CVD or ALD, in some embodiments. The thickness of the dummy gate dielectric layer 215 is in a range from about 1 nm to about 3 nm in some embodiments.

Then, a polysilicon layer 230 is formed over the dummy gate electrode layer 215, and further a hard mask layer is formed on the polysilicon layer. The hard mask layer is patterned into hard mask pattern 235 by suitable lithography and etching operations, as shown in FIGS. 9A-9C. The hard mask pattern 235 includes one or more layers of insulating material, such as silicon oxide and silicon nitride, in some embodiments.

FIG. 9A shows a perspective view, FIG. 9B is a cross sectional view along the Y direction and FIG. 9C is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. By using the hard mask pattern 235 as an etching mask, the polysilicon layer is patterned into dummy gate electrodes 230, as shown in FIGS. 9A-9C. In some embodiments, the width of the dummy gate electrode 230 is in a range from about 8 nm to about 20 nm.

FIG. 10A shows a perspective view, FIG. 10B is a cross sectional view along the Y direction and FIG. 10C is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Sidewall spacers 240 are formed on opposing side faces of the dummy gate electrodes 230. The sidewall spacers 240 include one or more layers of insulating material, such as silicon oxide, silicon nitride and silicon oxynitride. Moreover, source/drain epitaxial layers 250 are formed over source/drain regions of the fin structures 210. The source/drain epitaxial layer 250 includes SiP, SiAs, SiGeP, SiGeAs, GeP, GeAs, and/or SiGeSn or other suitable material for an n-type FET, and SiB, SiGa, SiGeB, SiGeGa, GeB, GeGa and/or SiGeSn or other suitable material for a p-type FET. The thickness of the source/drain epitaxial layers 250 is in a range from about 3 nm to about 8 nm in some embodiments. In some embodiments, an alloy layer, such as, a silicide layer, is formed over the source/drain epitaxial layers 250.

FIG. 11A shows a perspective view, FIG. 11B is a cross sectional view along the Y direction and FIG. 11C is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Subsequently, a contact etch stop layer (CESL) 245 and an interlayer dielectric layer 260 are formed, and a planarization operation, such as a CMP operation, is performed to exposed upper surfaces of the dummy gate electrodes 230, as shown in FIGS. 11A-11C.

In some embodiments, the CESL layer 245 is made of a silicon nitride based material, such as SiN and SiON, and the interlayer dielectric layer 260 is made of a silicon oxide based material, such as SiO₂ or a low-k material. In some embodiments, an annealing operation is performed after the interlayer dielectric layer is formed.

FIG. 12A shows a perspective view, FIG. 12B is a cross sectional view along the Y direction and FIG. 12C is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Then, the dummy gate electrodes 230 and the dummy gate dielectric layer 215 are removed by using dry and/or wet etching, thereby forming gate spaces 265, as shown in FIGS. 12A-12C. Further, in the gate spaces 265, an interfacial layer 271 and a ferroelectric dielectric layer 270 are formed as shown in FIGS. 12A-12C. In some embodiments, a seed dielectric layer (not shown) is formed between the interfacial layer 271 and the dielectric layer 270. As set forth above, the interfacial layer 271 is made of silicon oxide, the seed dielectric layer is made of ZrO₂, and the dielectric layer 270 is a Zr doped HfO₂ layer.

FIG. 13A shows a perspective view, FIG. 13B is a cross sectional view along the Y direction and FIG. 13C is a cross sectional view along the X direction, showing one of various stages of the manufacturing operation according to an embodiment of the present disclosure. Then, similar to the operations described with FIGS. 2A-3F, a capping layer 281 (see, FIG. 13D) is formed, and an annealing operation is performed to convert the amorphous HfO₂ layer to an orthorhombic HfO₂ layer. Further, a gate electrode 280 is formed, as shown in FIGS. 13A-13C. The capping layer and the gate electrode may be formed using a suitable process such as ALD, CVD, PVD, plating, or combinations thereof. After the conductive materials for the gate electrode are formed, a planarization operation, such as CMP, is performed to remove excess materials above the interlayer dielectric layer 260.

FIG. 13D shows an enlarged cross sectional view of a top portion of the fin structure of FIG. 13C. In some embodiments, the silicon substrate 200 is a (100) substrate, and thus the top of the fin structure 210 has a (100) orientation and side faces of the fin structure 210 have a (110) orientation. The interfacial layer 271 is formed on the fin structure 210, a ferroelectric dielectric layer 270 is formed on the interfacial layer 271, and a capping layer 281 similar to the capping layer 40 of FIGS. 2A-3F is formed on the ferroelectric layer 270.

As set forth above, the ferroelectric dielectric layer 270 is, for example, a Zr doped HfO₂ layer. The polarization P of the Zr doped HfO₂ is parallel to the c axis of orthorhombic structure. When the Zr doped HfO₂ is (111) oriented, the total polarization is P/√3.

In the present disclosure, since the capping layer 40/281 and/or the seed dielectric layer 25 are used to control the crystal orientation of the Zr doped HfO₂ layer, the grain orientation of the Zr doped HfO₂ formed on the top and side faces of the fin structure 210 is (111), as shown in FIG. 13D. The orthorhombic crystal phase identification and (111) orientation identification of specific crystal grain can be determined by the precession electron diffraction (PED) technique. Accordingly, it is possible to achieve a largest ferroelectric effect by controlling the doped HfO₂ polarization to be parallel with the external electric-field from the gate electrode 280 for all directions.

After forming the gate structures, further CMOS processes are performed to form various features such as additional interlayer dielectric layers, contacts/vias, interconnect metal layers, and passivation layers, etc.

FIGS. 14A-14D show other manufacturing operations for an NC FinFET in accordance with some embodiments of the present disclosure. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements. It is understood that additional operations can be provided before, during, and after processes shown by FIGS. 14A-15D, and some of the operations described below can be replaced or eliminated, for additional embodiments of the method. The order of the operations/processes may be interchangeable. Material, configuration, dimensions and/or processes the same as or similar to the foregoing embodiments described with respect to FIGS. 1A, 2A-3F and 7A-13C may be employed in the following embodiments, and detailed explanation thereof may be omitted.

As shown in FIG. 14A, the fin structures 320 are patterned by using the hard mask pattern 312, and the isolation insulating layer 325 is formed. Then, a dummy gate dielectric layer (not shown) and a polysilicon layer 332 are formed over the fin structures 320, and further a hard mask pattern 334 is formed on the polysilicon layer 332, as shown in FIG. 14B. The hard mask pattern 324 includes one or more layers of insulating material, such as silicon oxide and silicon nitride.

By using the hard mask pattern 334 as an etching mask, the polysilicon layer 332 is patterned into a dummy gate electrode 332. Further, sidewall spacers 336 are formed on opposing side faces of the dummy gate electrode 332, and an interlayer dielectric layer 342 is formed, as shown in FIG. 14C. The sidewall spacers 336 include one or more layers of insulating material, such as silicon oxide, silicon nitride and silicon oxynitride, and the interlayer dielectric layer 342 includes one or more layers of insulating material such as silicon oxide based material such as silicon dioxide (SiO₂) and SiON. The material of the sidewall spacers 333 and the material of the interlayer dielectric layer 342 are different from each other, so that each of these layers can be selectively etched. In one embodiment, the sidewall spacer 333 is made of SiOCN, SiCN or SiON and the interlayer dielectric layer 342 is made of SiO₂.

Then, the dummy gate electrode 332 and the dummy gate dielectric layer are removed by using dry and/or wet etching, thereby forming a gate space 333, as shown in FIG. 14D.

In the gate space, a first gate dielectric layer 303 and a first gate electrode 304 are formed as shown in FIGS. 15A and 15B. After the conductive material is formed over the first gate dielectric layer 303, a planarization operation, such as CMP, is performed to form the first gate electrode 304. The first gate dielectric layer 303 is made of, for example, a high-k dielectric material, and the first gate electrode 304 is made of, for example, a conductive material such as TiN or other metal material. Further, an etch-back operation is performed to reduce the height of the first gate dielectric layer 303 and the first gate electrode 304. The conductive material may be formed using a suitable process such as ALD, CVD, PVD, plating, or combinations thereof.

Then, a ferroelectric dielectric layer 305 and a second gate electrode 306 are formed in the gate space 333, as shown in FIGS. 15C and 15D. A ferroelectric dielectric layer 305 is formed by the operations described with respect to FIGS. 2A-3F. A conductive material is formed over the ferroelectric dielectric layer 303. After the conductive material is formed over the ferroelectric dielectric layer 305, a planarization operation, such as CMP, is performed to form the second gate electrode 306, as show in FIGS. 15C and 15D.

After forming the gate structures, further CMOS processes are performed to form various features such as additional interlayer dielectric layers, contacts/vias, interconnect metal layers, and passivation layers, etc.

Other methods and structures for manufacturing MIMIS NC FETs are described in U.S. patent application Ser. Nos. 15/476,221 and 15/447,479, the entire contents of each of which are incorporated herein by reference.

It will be understood that not all advantages have been necessarily discussed herein, no particular advantage is required for all embodiments or examples, and other embodiments or examples may offer different advantages.

For example, in the present disclosure, a doped HfO₂ having an orthorhombic crystal phase is employed for an NC FET. By using a capping metallic layer during an annealing operation, it is possible to effectively convert an amorphous structure of the as-deposited HfO₂ layer to an orthorhombic crystal structure. As compared to other perovskite ferroelectric films (such as, PZT or BaTiO₃), the ferroelectric HfO₂ disclosed herein can maintain polarization without degradation down to 3 nm.

In accordance with an aspect of the present disclosure, in a method of manufacturing a negative capacitance structure, in a method of manufacturing a negative capacitance structure, a dielectric layer is formed over a substrate. A first metallic layer is formed over the dielectric layer. After the first metallic layer is formed, an annealing operation is performed followed by a cooling operation. A second metallic layer is formed over the dielectric layer. After the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase, and the first metallic film includes a (111) oriented crystalline layer. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfO₂ doped with one or more selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfO₂ doped with Zr and includes a (111) oriented crystalline layer. In one or more of the foregoing or following embodiments, the annealing operation is performed at a temperature in a range from 700° C. to 1000° C. in an inert gas ambient. In one or more of the foregoing or following embodiments, the second metallic layer is formed after the cooling operation. In one or more of the foregoing or following embodiments, the first metallic layer includes TiN doped with Si. In one or more of the foregoing or following embodiments, the second metallic layer is TaN. In one or more of the foregoing or following embodiments, the forming a dielectric layer includes alternately forming one or more HfO₂ layers and one or more ZrO₂ layers over a substrate. In one or more of the foregoing or following embodiments, the dielectric layer as formed is amorphous.

According to another aspect of the present disclosure, in a method of manufacturing a negative capacitance structure, a seed dielectric layer is formed over a substrate. A dielectric layer is formed over the seed dielectric layer. A first metallic layer is formed over the dielectric layer. After the first metallic layer is formed, an annealing operation is performed followed by a cooling operation. After the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase, and the seed dielectric layer becomes a dielectric layer including an orthorhombic crystal phase. In one or more of the foregoing or following embodiments, the seed dielectric layer is ZrO₂. In one or more of the foregoing or following embodiments, the dielectric layer includes HfO₂ containing Zr. In one or more of the foregoing or following embodiments, the forming a dielectric layer includes alternately forming one or more HfO₂ layers and one or more ZrO₂ layers over a substrate. In one or more of the foregoing or following embodiments, the annealing operation is performed at a temperature in a range from 700° C. to 1000° C. in an inert gas ambient. In one or more of the foregoing or following embodiments, the capping metallic layer includes TiN doped with Si. In one or more of the foregoing or following embodiments, in the method, a second metallic layer is further formed over the dielectric layer. In one or more of the foregoing or following embodiments, the second layer is formed after the cooling operation. In one or more of the foregoing or following embodiments, in the method, an interfacial oxide layer is further formed over the substrate before the seed dielectric layer is formed.

In accordance with another aspect of the present disclosure, in a method of manufacturing a negative capacitance fin field effect transistor (NC-FinFET), a dummy gate structure is formed over a fin structure. A source/drain structure is formed over the fin structure on opposing sides of the dummy gate structure. An interlayer dielectric layer is formed over the source/drain structure. The dummy gate structure is removed, thereby exposing a channel region of the fin structure. An interfacial layer is formed over the exposed fin structure. A dielectric layer is formed over the interfacial layer. After the dielectric layer is formed, an annealing operation is performed followed by a cooling operation. A gate electrode including one or more metallic layers is formed. After the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase. At least one of a bottom crystal structure control layer between the interfacial layer and the dielectric layer and an upper crystal structure control layer between the dielectric layer and the gate electrode is provided. In one or more of the foregoing or following embodiments, the dielectric layer includes Zr doped HfO₂.

In accordance with one aspect of the present application, a negative capacitance structure includes a channel layer made of a semiconductor, a ferroelectric dielectric layer disposed over the channel layer, and a gate electrode layer disposed over the ferroelectric dielectric layer. The ferroelectric dielectric layer includes a (111) oriented orthorhombic crystal. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfO₂ doped with one or more selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfO₂ doped with Zr and includes a (111) oriented crystalline layer. The orthorhombic crystal phase identification and (111) orientation identification of specific crystal grain can be detected by the PEDz technique. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer further includes Ti in an amount of 2-5 mol %. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer further includes Al in an amount of 5-7 mol %. In one or more of the foregoing or following embodiments, the gate electrode layer includes a Si-doped TiN layer in contact with the ferroelectric dielectric layer. In one or more of the foregoing or following embodiments, the Si-doped TiN layer is (111) orientated. In one or more of the foregoing or following embodiments, the negative capacitance structure further includes an interfacial layer disposed on the channel layer, and a seed dielectric layer disposed on the interfacial layer. In one or more of the foregoing or following embodiments, the seed dielectric layer includes ZrO₂.

In accordance with another aspect of the present application, a negative capacitance field effect transistor (NC-FET) includes a channel layer made of a semiconductor, an interfacial layer disposed on the channel layer, a ferroelectric dielectric layer disposed over the interfacial layer, and a gate electrode layer disposed over the ferroelectric dielectric layer. The ferroelectric dielectric layer includes a (111) oriented orthorhombic crystal. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfO₂ doped with one or more selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer includes HfZrO₂. In one or more of the foregoing or following embodiments, at least one of a bottom crystal structure control layer between the interfacial layer and the dielectric layer and an upper crystal structure control layer between the dielectric layer and the gate electrode is formed. In one or more of the foregoing or following embodiments, the bottom crystal structure control layer includes ZrO₂. In one or more of the foregoing or following embodiments, the upper crystal structure control layer includes Si-doped TiN. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer further includes Ti in an amount of 2-5 mol %. In one or more of the foregoing or following embodiments, the NC-FET is an n-type FET and the work function adjustment layer includes TiAl. In one or more of the foregoing or following embodiments, the ferroelectric dielectric layer further includes Al in an amount of 5-7 mol %.

In accordance with another aspect of the present application, a negative capacitance field effect transistor (NC-FET) includes a channel layer made of a semiconductor, a first dielectric layer disposed over the channel layer, a first conductive layer disposed over the first dielectric layer, a second dielectric layer disposed over the first conductive layer, and a gate electrode layer disposed over the second dielectric layer. The ferroelectric dielectric layer includes a (111) oriented orthorhombic crystal. In one or more of the foregoing or following embodiments, the NC-FET further comprises an interfacial layer disposed on the channel layer. At least one of a bottom crystal structure control layer between the interfacial layer and the first dielectric layer and an upper crystal structure control layer between the first dielectric layer and the first conductive layer is provided.

The foregoing outlines features of several embodiments or examples so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments or examples introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method of manufacturing a negative capacitance structure, the method comprising: forming a dielectric layer over a substrate; forming a first metallic layer over the dielectric layer; after the first metallic layer is formed, performing an annealing operation followed by a cooling operation; and forming a second metallic layer on the first metallic layer, wherein: after the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase, and the first metallic layer includes a single layer of TiN doped with Si, and comprises a (111) oriented crystalline layer.
 2. The method of claim 1, wherein the ferroelectric dielectric layer includes HfO₂ doped with one or more selected from the group consisting of Si, Zr, Al, La, Y, Gd and Sr.
 3. The method of claim 1, wherein the ferroelectric dielectric layer includes a single layer of HfO₂ doped with Zr and comprises a (111) oriented crystalline layer.
 4. The method of claim 1, wherein the annealing operation is performed at a temperature in a range from 700° C. to 1000° C. in an inert gas ambient.
 5. The method of claim 1, wherein the second metallic layer is formed after the cooling operation.
 6. The method of claim 1, wherein the second metallic layer is TaN.
 7. The method of claim 1, wherein the forming a dielectric layer includes alternately forming HfO₂ layers and ZrO₂ layers over a substrate.
 8. The method of claim 1, wherein the dielectric layer as formed is amorphous.
 9. The method of claim 1, wherein the ferroelectric dielectric layer includes HfO₂ doped Ti in an amount of 2 mol % to 5 mol %.
 10. A method of manufacturing a negative capacitance structure, the method comprising: forming a seed dielectric layer over a substrate; performing a first annealing operation on the seed dielectric layer; after the first annealing operation, forming a dielectric layer over the seed dielectric layer; forming a first metallic layer over the dielectric layer; and after the first metallic layer is formed, performing a second annealing operation followed by a cooling operation, wherein: after the cooling operation, the dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase, and the seed dielectric layer becomes a ferroelectric dielectric layer including an orthorhombic crystal phase.
 11. The method of claim 10, wherein the seed dielectric layer is ZrO₂.
 12. The method of claim 10, wherein the dielectric layer includes HfO₂ containing Zr.
 13. The method of claim 10, wherein the forming a dielectric layer includes alternately forming HfO₂ layers and ZrO₂ layers over a substrate.
 14. The method of claim 10, wherein the second annealing operation is performed at a temperature in a range from 700° C. to 1000° C. in an inert gas ambient.
 15. The method of claim 10, wherein the capping metallic layer includes TiN doped with Si.
 16. The method of claim 10 further comprising forming a second metallic layer over the dielectric layer.
 17. The method of claim 16, wherein the second layer is formed after the cooling operation.
 18. The method of claim 10, further comprising forming an interfacial oxide layer over the substrate before the seed dielectric layer is formed.
 19. A negative capacitance field effect transistor (NC-FET), comprising: a channel layer made of a semiconductor; a ferroelectric dielectric layer disposed over the channel layer; a metallic film comprising a (111) oriented crystalline layer; and a gate electrode layer disposed over the ferroelectric dielectric layer, wherein the ferroelectric dielectric layer includes a single layer of HfZrO₂ comprising a (111) oriented orthorhombic crystal.
 20. The NC-FET of claim 19, further comprising a silicon oxide layer having a thickness in a range from 0.5 nm to 1.5 nm between the channel layer and the ferroelectric dielectric layer. 